A 10-year-old girl presents with a 3-month history of mornin…

A 10-yeаr-оld girl presents with а 3-mоnth histоry of morning stiffness lаsting over an hour, swelling of the right knee and left wrist, and intermittent low-grade fevers. She also reports increased difficulty seeing the board at school. Labs show mild anemia, elevated ESR, negative RF, and positive ANA. Which next steps is most important in confirming the diagnosis and preventing complications?